Make share intent modal to make "signed in as" shown. (#4611)

* Make share intent modal to make "signed in as" shown.

* fix glitch on mobile.

app/controllers/shares_controller.rb

 # frozen_string_literal: true
 
 class SharesController < ApplicationController
-  layout 'public'
+  layout 'modal'
 
   before_action :authenticate_user!
+  before_action :set_body_classes
 
   def show
     serializable_resource = ActiveModelSerializers::SerializableResource.new(InitialStatePresenter.new(initial_state_params), serializer: InitialStateSerializer)
@@ -22,4 +23,8 @@ class SharesController < ApplicationController
       text: params[:text],
     }
   end
+
+  def set_body_classes
+    @body_classes = 'compose-standalone'
+  end
 end

app/javascript/styles/containers.scss

@@ -53,6 +53,7 @@
     box-sizing: border-box;
 
     @media screen and (max-width: 400px) {
+      width: 100%;
       margin-top: 0;
       padding: 20px;
     }